A Worldwide Map ofPlasmodium falciparumK13-Propeller Polymorphisms

Abstract

BACKGROUND Recent gains in reducing the global burden of malaria are threatened by the emergence of Plasmodium falciparum resistance to artemisinins. The discovery that mutations in portions of a P. falciparum gene encoding kelch (K13)–propeller domains are the major determinant of resistance has provided opportunities for monitoring such resistance on a global scale. METHODS We analyzed the K13-propeller sequence polymorphism in 14,037 samples collected in 59 countries in which malaria is endemic. Most of the samples (84.5%) were obtained from patients who were treated at sentinel sites used for nationwide surveillance of antimalarial resistance. We evaluated the emergence and dissemination of mutations by haplotyping neighboring loci. RESULTS We identified 108 nonsynonymous K13 mutations, which showed marked geographic disparity in their frequency and distribution. In Asia, 36.5% of the K13 mutations were distributed within two areas — one in Cambodia, Vietnam, and Laos and the other in western Thailand, Myanmar, and China — with no overlap. In Africa, we observed a broad array of rare nonsynonymous mutations that were not associated with delayed parasite clearance. The gene-edited Dd2 transgenic line with the A578S mutation, which expresses the most frequently observed African allele, was found to be susceptible to artemisinin in vitro on a ring-stage survival assay. CONCLUSIONS No evidence of artemisinin resistance was found outside Southeast Asia and China, where resistance-associated K13 mutations were confined. The common African A578S allele was not associated with clinical or in vitro resistance to artemisinin, and many African mutations appear to be neutral.

Molecular Epidemiology of Plasmodium falciparum kelch13 Mutations in Senegal Determined by Using Targeted Amplicon Deep Sequencing

“…The predominant polymorphisms previously reported in Senegal are alleles K189T and K189N, outside the propeller domain (25,26), consistent with our own findings (Table S1). The mutant allele A578S, which is not associated with artemisinin resistance, has been reported in multiple regions in Africa (18,19,24,28) (Table S2). In comparison, we observed a different amino acid substitution at this codon position in a single sample, from alanine (A) to aspartic acid (D) (Table S2).…”

Plasmodium falciparum Resistance to Artemisinin Derivatives and Piperaquine: A Major Challenge for Malaria Elimination in Cambodia

“…A worldwide map of P. falciparum K13-propeller polymorphism was recently published from a study involving 41 partner institutions and 14,037 samples collected from 163 sites (in 59 countries in which malaria is endemic), providing a global overview of the distribution of artemisinin resistance and fundamental data for drug policy makers and future surveillance activities. 59 The main findings of the KARMA study (K13 Artemisinin Resistance Multicenter Assessment) suggest that artemisinin resistance remains confined to southeast Asia (including Cambodia, PDR of Laos, Thailand, Vietnam, and Myanmar) and China. In these two regions, the proportions of parasites with K13 mutations were estimated at 51.8% (95% CI: 48.5-55.3%) and 25.6% (95% CI: 19.3-33.3%), respectively.…”

Genetic markers of artemisinin resistance in Plasmodium spp. parasites

“…Pfk13 was one of a few loci in the genome of the cultureadapted Tanzanian P. falciparum isolate F32 that, during this extensive selection process, had accumulated mutations in concert with decreasing DHA susceptibility as measured by the RSA. Alone among these few loci, mutations in pfk13 were also found to correlate with ex vivo DHA susceptibility of Cambodian parasites in the RSA, although the exact mutation identified in mutant F32 parasites has still not been encountered in any wild P. falciparum isolates to date [9]. The identification of key variants of pfk13 that correlate both with slow clearance in patients receiving artesunate monotherapy [3] and with ex vivo RSA data [6] has enabled subsequent research on pfk13.…”

“…• studies of the distribution of polymorphisms in the field, particularly in Africa [9][10][11][12][13];…”